Laser dot may be duplicated by Diffractive Optical Element (DOE) to generate multiple same light dots and to be projected as a distribution pattern of light dots at a distance. The distribution pattern, like to a jigsaw, can be constituted a larger projecting pattern by piecing multitudes of them together. However, such a projecting pattern with the duplicated distribution patterns may cause error in depth estimation when it is applied to structured-light application. Accordingly, the projecting pattern with the duplicated distribution patterns needs to be improved if it would be like to apply to structured-light fields.